Low residual stress SiC coatings on C/CA composites by a strategy of matching their expansion behaviors to improve thermal shock resistance

Abstract

The poor thermal shock resistance of coated C/CA composites limits the applications with rapid temperature fluctuations due to the huge thermal mismatch between the coating and the substrate. A facile strategy of tailoring coefficient of thermal expansion (CTE) of C/CA is proposed to match their thermal deformation behaviors. The optimized C/CA by heat treatment has a positive correlation between CTE and temperature, and thus the as-prepared SiC coating has a decreased macroscopic residual strain of 80.7% due to their coordinated thermal response compared to the original C/CA. Meanwhile, benefited from the structural improvement of larger pore size and higher degree of graphitization of C/CA, a significantly decreased tensile stress of 60.3% in the coating is achieved due to the formation of small SiC spheres in the carbon network. Resultantly, the coated C/CA shows remarkably improved thermal shock resistance with narrower and fewer microcracks, and lower mass and linear cyclic ablation rates of 0.252 mg/s and 0.607 μm/s, respectively.